Disturbing shutdown while under way

[heygibb]

Recently, I experienced something new for me. I left a restaurant parking lot normally. As I accelerated, the engine seemed to cut off, sputtered (like a bad vacuum leak) and then cut off totally. I was able to get it restarted and haven't had this happen again since. I don't want to get stranded somewhere out of town so instead of ignoring it, I want to find the problem and a remedy. My mileage is 164k and I drive less than 4000 a year. I replaced the coils a couple of years ago but haven't put many miles on the car since. I haven't gone through the onboard diagnostics yet, but is a failing ECM a likely source of the problem? Does an ECM fail intermittently or all at once? The car is 29 years old and still has OEM ECM. Any help much appreciated.

Tim

[2seater]

It is difficult to diagnose when it won't stay broken, but from those symptoms, I would bet on the Crank sensor or the ICM under the coils. Did the tachometer on the dash quit at the same time or perhaps just before?

[heygibb]

I did not notice the tach reading, to be honest. I was too occupied w/ pulling over safely and keeping my "freak out" mode under control.

I replaced the ICM when I replaced the coils. That might not mean a thing, but just letting you know. I've replaced the crank position sensor several times so I am familiar with that. I need to get my files out to see mileage when I last did it. Maybe all it needs is a check to see if it is still snug and in  position.

[2seater]

It sounds like you have addressed my likely culprits, but it pays to double check all the connections and harness for issues. I am curious about the several CPS replacements? They are pretty reliable unless damaged so multiple replacements sounds unusual. Are any codes present? I have not had any issues with the ECM, so hard to say symptoms, but it is the brains behind the engine operation, and sure never hurts to have a known good spare. Fuel, air and spark, just need to narrow the list, easier said than done sometimes🤔

[heygibb]

I was just headed out to run onboard diagnostics. From my files, a bad cam position sensor (not needed to start engine) will reduce engine performance and produce Code 41. I'll look for that.

12/15, ~156k miles

replaced crank position sensor, cam position sensor, coils...all new

ICM from U pull it yard

re the CPS replacements...I think I"ve replaced it 3 times in 29 years. I remember damaging one, as it moved off center when I snugged it down...if memory serves.

[bikemikey]

If everything else checks out, you might check the PCV valve. Sometimes they will stick if they get too dirty and act like a vacuum leak.  It probably would not hurt to change it anyway if it is old. 

[DAVES89]

I would go to the You Pick yard and get two ICMs [Ignition Control Module]. Try them both and keep one for a back up. They are cheap and most likely to fail. Be sure to try both to make sure they work.

[heygibb]

I have one in my trunk from my last trip to the U pull it yard. I'll probably wait and see if I have another failure before swapping.But it would be wise to look for other replacements while it's on my mind. I have a list of GM vehicles that have similar 3800L engines. I need to do an inventory check on the yard I usually go to and locate where they are. It's easy to spend half a day looking.

I'll check the PCV. I've put 9k miles on car since I replaced it, but it's worth checking. I'll be surprised if it's gunked up.

Results of OBD are :

after warmed up, first read I get E 034, E 064 and E 065 as current

after clearing data, all I get is E 034...I don't remember what it refers to so I'll have to check into it. I believe the 064, and 065 codes are EGR related. They didn't reappear after clearing the codes. I have a delete plate under my EGR so that is probably related to that. I usually ignore those codes. Within the past few months, I took ~8-900 mile road trip and got 28 mpg, w/ no issues on the trip.

 

[2seater]

1 hour ago, DAVES89 said:

I would go to the You Pick yard and get two ICMs [Ignition Control Module]. Try them both and keep one for a back up. They are cheap and most likely to fail. Be sure to try both to make sure they work.

Good advice here. From the previous descriptions, it sounds like all parts previously replaced have been new except the ICM?

[heygibb]

Correct.

 

[heygibb]

My PCV was clean as a whistle...even more so after a dose of carb cleaner through it. It's a PITA to remove and replace though. On a side note, the edges of the rubber hose it connects to show some splitting and was wondering if anyone had ever replaced that section of hose? Does it just pull out w/ a little twist/pull?

I found some good info on my code 034 in the included link. I'll clean the MAF sensor as described and check my air filter, and leave it at that. If the issue pops up again, I'll replace the ICM. In the meantime, I'll go looking for more. Thanks for the help.

 

[heygibb]

It's taken a while, but I am changing my ICM, as suggested. I had another episode of "resistance to starting" after a 6 mile trip. It brought back an episode from 8 yrs ago where after a 50 mile trip, my car would not restart until the engine cooled off. The heat buildup appears to be a catalyst to the failure.

My current ICM is a pull from a salvage yard from a 93 Olds, I believe. So it has performed for 25 yrs, give or take. I use the Delco coil configuration, not the Magnavox. When I installed it, I spaced the mounting surface away from the block w/ washers, thinking air flow, even if minute, between the two surfaces would reduce heat transfer to the ICM.

On this repair, I was curious what the consensus is re the mount interface to the block. Would using the washer spacer trick, with dielectric grease, be optimal? Washers alone? Full mating of the two surfaces, w/out washers, with dielectric grease?

I've attached a pic of what I've been running with since October, 2015.

[DAVES89]

I don't use washers as my thought is as much surface area as possible is better. So I cleaned both the top of the plate and the bottom of the ICM first with sandpaper and then carb cleaner. 

[heygibb]

That's interesting. Full contact would transfer more heat from the block to the ICM, it would seem. At the same time, it would help insure proper grounding, I suppose, but I'm guessing the bolts themselves serve as the main grounding point.

Do you use dielectric grease between the two parts? I've read where some people use it.

[DAVES89]

I don't try to out think the engineers at GM. If that is the way they designed it that's what I try to do. Can't remember if I used dielectric grease there, but I did use it on the connector.

[heygibb]

Good point.Thanks, Dave

[SeanR]

On 3/2/2019 at 9:37 AM, heygibb said:

Recently, I experienced something new for me. I left a restaurant parking lot normally. As I accelerated, the engine seemed to cut off, sputtered (like a bad vacuum leak) and then cut off totally. I was able to get it restarted and haven't had this happen again since. I don't want to get stranded somewhere out of town so instead of ignoring it, I want to find the problem and a remedy. My mileage is 164k and I drive less than 4000 a year. I replaced the coils a couple of years ago but haven't put many miles on the car since. I haven't gone through the onboard diagnostics yet, but is a failing ECM a likely source of the problem? Does an ECM fail intermittently or all at once? The car is 29 years old and still has OEM ECM. Any help much appreciated.

Tim

 

Mine is doing this too in the past few weeks. Im trying to find a pattern, but I think it happens in wet road conditions and when I take it to car wash with under spray. It was driving fine till I took it to the car wash, then it would just randomly buck and die unexpectedly. It would restart, but had me concerned about trying to drive it back home on a busy highway, so I had it towed home and havent investigated it. Like yourself, I have also replaced the coil a few years ago and the crank sensor behind the HBalancer. I did clean up airflow sensor with electrical spray. Definitely trying to attack this from cheapest to most expensive.

[heygibb]

Sean, did you replace the ICM under the coils, too? I am pretty sure that was my problem.  The one I removed had a buildup of a dried substance along the edges of where the harness polugged into it. It's an indicator of part failure, I believe.

From my experience, I associate the failure with a hot engine. It only happens to me when I'm on the road away from my neighborhood store runs. After the engine struggles to stay running, if at all, I let it cool and all is well.

Good luck w/ your diagnosis.

[SeanR]

On 3/28/2019 at 11:31 PM, heygibb said:

Sean, did you replace the ICM under the coils, too? I am pretty sure that was my problem.  The one I removed had a buildup of a dried substance along the edges of where the harness polugged into it. It's an indicator of part failure, I believe.

From my experience, I associate the failure with a hot engine. It only happens to me when I'm on the road away from my neighborhood store runs. After the engine struggles to stay running, if at all, I let it cool and all is well.

Good luck w/ your diagnosis.

 

Sorry for the much delayed response. I ended up replacing with a 91+ ICM/Coil unit from a later GM car and never had the problem since! Best upgrade an owner can do.

[heygibb]

I'd forgotten all about this post, so I enjoyed your response.

More recently, my car would struggle to start, randomly. It reminded me of a vac leak. I checked all the rubber hoses, and there was no dry rot, splits or loose connections. It wasn't until I looked at the hard plastic vac line going into the firewall on the passenger side, that I found it almost broken off at the check valve. It would line up enough to get the engine running occasionally. Frustrating, to say the least. It's something you need to keep an eye on if you haven't before now.

Here is a link to a good remedy for the brittle nature of the HVAC line, and performance of the check valve.